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Lehr, C. G.

Publications and source records attributed to Lehr, C. G..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Smithsonian Astrophysical Observatory laser tracking systems

The four SAO laser satellite-ranging systems, located in Brazil, Peru, Australia, and Arizona, have been in operation for more than five years and have provided ranging data at accuracy levels of a meter or better. The paper examines system hardware (laser transmitter, the electronics, mount, photoreceiver, minicomputer, and station timing) and software (prediction program, calibration programs, and data handling and quick-look programs) and also considers calibration, station operation, and system performance.

Pearlman, M. R.↗
NASA NTRS1977

National Geodetic Satellite Program, Part II: Smithsonian Astrophysical Observatory

A sequence of advances in the determination of geodetic parameters presented by the Smithsonian Astrophysical Observatory are described. A Baker-Nunn photographic system was used in addition to a ruby-laser ranging system to obtain data for refinement of geodetic parameters. A summary of the data employed to: (1) derive coordinates for the locations of various tracking stations; and (2) determine the gravitational potential of the earth, is presented.

Arnold, D. A.↗
NASA NTRS1975

Photoreceiver efficiency measurements

The efficiency and other related parameters of Smithsonian Astrophysical Observatory's four laser receivers were measured at the observing stations by oscilloscope photography. If the efficiency is defined as the number of photoelectrons generated by the photomultiplier tube divided by the number of photons entering the aperture of the receiver, its measured value is about 1% for the laser wavelength of 694 nm. This value is consistent with the efficiency computed from the specified characteristics of the photoreceiver's optical components.

Lehr, C. G.↗
NASA NTRS1974

Laser pulse analysis

The paper describes attempts to improve the satellite range measurements obtained with a laser ranging system. The transmitted and received ranging pulses were displayed on an oscilloscope and photographed. The pulse images were measured and the measurement data analyzed by computer. The range errors are reduced by utilizing information contained in the shapes of the return pulses. The problem of determining the center of the irregular return pulse is discussed. The results of the investigation show that the corrections made from the oscilloscope photographs improve the accuracy of the range measurements.

Lehr, C. G.↗
NASA NTRS1973

The statistics of laser returns from cube-corner arrays on satellite

A method first presented by Goodman is used to derive an equation for the statistical effects associated with laser returns from satellites having retroreflecting arrays of cube corners. The effect of the distribution on the returns of a satellite-tracking system is illustrated by a computation based on randomly generated numbers.

Lehr, C. G.↗
NASA NTRS1973

Laser pulse analysis

Methods are presented for locating threshold points by using laser pulse analysis. It was found that there are errors involved in the determination of each of these quantities, and an attempt was made to separate their effects on the overall range correction. Several series of corrected range measurements for fixed reflectors and satellites were obtained. Residuals were computed by fitting the range measurements to either fixed-reflector distances or short arcs of satellite orbits. Root mean square values of these residuals are presented.

Lehr, C. G.↗
NASA NTRS1972

Laser system of extended range

A pulsed laser system was developed for range measurements from the earth to retroreflecting satellites at distances up to that of the moon. The system has a transportable transmitter unit that can be moved from one location to another. This unit consists of a 0.2 m coude refractor and a high radiance, neodymium-glass, frequency doubled laser that operates in a single transverse mode. It can be used for lunar or distant satellite ranging at any observatory that has a telescope with an aperture diameter of about 1.5 m for the detection of the laser return pulses. This telescope is utilized in the same manner customarily employed for the observation of celestial objects. A special photometric package and the associated electronics are provided for laser ranging.

Lehr, C. G.↗
NASA NTRS1972

Transportable lunar-ranging system.

Description of a transportable transmitting unit for measuring distances to retroreflectors on the moon. The unit can be installed at any astronomical observatory where a large telescope is available to detect the received signal. The transmitter consists of a high radiance, frequency-doubled neodymium-glass laser and a coude optical system of moderate size. The measurements may eventually be used to study variations in the length of the earth's day, changes in the geographic location of the pole, and the drifting of the continents.

Lehr, C. G.↗
NASA NTRS1972

The SAO lunar laser.

The SAO lunar-ranging system is currently being installed at the Agassiz Observatory, Harvard, Massachusetts, USA. It employs a high-radiance neodymium-glass laser and a transmitting telescope whose aperture diameter is only 0.2 m. This telescope is a coude refractor specially built for the purpose, with tracking accuracy 1 second of arc. The receiving instrument is the 1.5-m telescope at the Agassiz Observatory. However, the laser transmitting unit can be moved to other locations where telescopes of similar size are available. Since the large telescope does not transmit the laser radiation, it remains in a normal mode of operation and the regular observing schedule is not disrupted. During routine operation, the receiver field will be larger than that of the transmitter, thus imposing less of a constraint on the tracking capability of the large optical instrument.

Lehr, C. G.↗
NASA NTRS1970

Laser satellite ranging

Laser range finding to satellite equipped with retroreflectors, noting accuracy dependence on signal strength

Lehr, C. G.↗